* syscalls.cc (_link): Make sure that newpath does not exist. Set errno if it

* syscalls.cc (_link): Make sure that newpath does not exist.  Set errno if it
does.
* cygheap.cc (init_cheap): Don't specify a load address for the heap.  It
doesn't work on #!*& Windows 9x.
(cygheap_init): Move GetUserName to memory_init.
* dcrt0.cc (dll_crt0_1): Call new memory_init functin, eliminate call to
heap_init.
* heap.cc (heap_init): Improve error output.
* heap.h: Correct some declarations.
* shared.cc (mount_table_init): Remove.
(memory_init): Renamed from shared_init.  Reorganize to accomodate strange
Windows 9x problems with cygheap/heap interaction.
* shared_info.h: Rename shared_init to memory_init.